[quick question] Why sync_wait a task returns a wrapped tuple?

[lixin-wei]

Hi I'm a novice to std::execution, I'm curious about the fowllowing example in this repo:

stdexec/examples/hello_coro.cpp

Lines 33 to 36 in 26d8565

	template <sender S1, sender S2>
	exec::task<std::optional<int>> async_answer2(S1 s1, S2 s2) {
	co_return co_await stopped_as_optional(async_answer(s1, s2));
	}

stdexec/examples/hello_coro.cpp

Line 46 in 26d8565

auto [i] = stdexec::sync_wait(async_answer2(just(42), just())).value();

why sync_wait returns a std::tuple<std::optional<int>> instead of std::optional<int> directly?

It's a little unintutive, is it designed intentionally for some purpose?

[maikel]

I think the answer is consistency. In the way it currently is, it is eaiser to use sync_wait in a generic context since it always returns a tuple. Note, that, in general, senders can complete with multiple values, whereas the exec::task has a single completion value type. Sync wait doesn't distinguish between single-value-senders and general senders and just transforms the result consistently.

[lixin-wei]

get it, thanks a lot!